Over the years considerable work has been devoted to additives for controlling (preventing or reducing) deposit formation in the fuel induction systems of spark-ignition internal combustion engines. In particular, additives that can effectively control fuel injector deposits, intake valve deposits and combustion chamber deposits represent the focal point of considerable research activities in the field and despite these efforts, further improvements are desired.
DIG technology is currently on a steep developmental curve because of its high potential for improved fuel economy and power. Environmentally, the fuel economy benefits translate directly into lower carbon dioxide emissions, a greenhouse gas that is contributing to global warming.
However, direct injection gasoline engines can encounter problems different from those of the conventional engines due to the direct injection of gasoline into the combustion chamber.
One of the major obstacles in DIG engine development was spark plug fouling. A narrow spacing configuration, where the fuel injector sat close to the spark plug, allowed easy fuel ignition as the fuel directly hit the plug. This caused soot to accumulate on the plug, eventually leading to fouling.
Another problem is related to the smoke exhausted mainly from the part of the mixture in which the gasoline is excessively rich, upon the stratified combustion. The amount of soot produced is greater than that of a conventional MPI engine, thus a greater amount of soot can enter the lubricating oil through combustion gas blow by.
Current generation DIG technologies have experienced deposit problems. Areas of concern are fuel rails, injectors, combustion chamber (CCD), crankcase soot loadings, and intake valves (IVD). Deposits in the intake manifold come in through the PCV valve and exhaust gas recirculation (EGR). Since there is no liquid fuel wetting the back of the intake valves, these deposits build up quite quickly.
However, as different engine types enter service worldwide, a fuel to power not only traditional multi-port fuel injected engines, but also gasoline direct injection engines will be required. The additives which work well as detergents in MPI engines will not necessarily work well DIG engines, and as such additional detergents prepared especially for DIG engines may be required as a “top-treat” type additive or as an after-market fuel supplement.
There are numerous references teaching fuel compositions containing detergent compounds such as U.S. Pat. No. 4,231,759, or blends of detergents, for example U.S. Pat. Nos. 5,514,190, 5,522,906, and 5,567,211. There are also references teaching fuel compositions containing succinimide compounds, for example, U.S. Pat. No. 6,548,458 B2, but not in combination with detergents. There are also references teaching fuel compositions containing polyamines, polyethers, or polyetheramines, for example, U.S. Pat. Nos. 5,089,029, 5,112,364, and 5,503,644, but not in combination with dispersants such as succinimide. Nor do any of these references teach the use of fuel compositions containing Mannich base or polyetheramine detergents in combination with succinimide compounds in direct injection gasoline engines or the impact the combination of these compounds has on deposits in these engines.